Along with an improvement in integration of LSIs, circuit line widths of semiconductor devices have become finer. As an example of a method for forming exposure masks (exposure masks used in steppers and scanners are also called reticles) that are used for forming circuit patterns in such semiconductor devices, an electron-beam writing technology having high resolution has been used.
For example, there are writing apparatuses that use multiple beams. The use of multiple beams can greatly improve the throughput because it enables irradiation with more beams at a time (in a single shot) than in the case where writing is performed using a single electron beam. In such multi-beam writing apparatuses, for example, multiple beams are formed by letting an electron beam emitted from an electron gun pass through an aperture member having a plurality of apertures. Blanking control is performed on each of the beams. Unblocked beams are each reduced by an optical system, and a substrate placed on a movable stage is irradiated with the resulting beams.
Multi-beam writing apparatuses include a main deflector and a sub deflector that deflect beams to determine the beam irradiation position on a substrate. The main deflector collectively aligns the multiple beams to a predetermined position on a substrate, and the sub deflector deflects the beams so that beam pitches are filled.
Such multi-beam writing apparatuses write a pattern of a desired figure shape by emitting a plurality of beams at a time and linking the beams that are formed as a result of the beams passing through the same or different apertures of an aperture member. Since the shape of the entire multi-beam image with which the substrate is irradiated appears as the stitching accuracy of the written figures, it is essential to adjust a reduction ratio (magnification ratio) and a distortion of the entire multi-beam image.
Since the reduction ratio or the like of the entire multi-beam image is adjusted based on the beam shape, the beam shape needs to be accurately measured. The beam shape is measured by scanning a reflection mark on the stage while sequentially switching between beams to be ON and by detecting the position of the beam.
However, there is an issue in that when the reflection mark on the stage is scanned, an amount of beam deflection applied by the main deflector increases, which changes the path of the beam and distorts the beam shape and consequently decreases the accuracy of beam shape measurement.